Tool arrangement for machining restricted spaces, e.g. for internal turning

ABSTRACT

In a tool arrangement, an end part of a holder shaft is provided with a seat which provides a stable support for a cutter insert in at least two of the principal directions utilized in a machining operation. Stresses imposed on the cutter insert during the machining operation are transferred in an effective fashion to the shaft. The arrangement includes at least one tightenable fastening device which, after tightening, engages with the cutter insert and forces it against at least one surface of the seat. The cutter insert has stop parts with which the fastening device is intended to engage only after the cutter insert, through displacement relative to the seat on the shaft and whilst the cutter insert still in contact with the seat, has reached its operating position.

BACKGROUND OF THE INVENTION

The invention relates to an arrangement for tools for cutting andmachining, in particular, turning in restricted spaces, for example,turning inside a hole or in a tube-like workpiece.

Tools intended for operations of this kind are previously known and, asa general rule, comprise a cutter of hardened metal material, carbidematerial or the like attached to the end of a shaft by means of athreaded connection. To remove a worn cutter so a new one can beinstalled, it is necessary to fully loosen a screw passing through thecutter before the cutter can be removed or attached. In this replacementoperation, it is necessary to keep track not only of the cutter, whichin many cases is very small, but also of the loose screw, and to fit thelatter into a threaded hole in the shaft. This makes the operationdifficult so the machine operator tends to use a cutter for an excessiveperiod in order to avoid having to change the cutter.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a novel arrangementwhich securely grips the cutter and facilitates the replacement of thecutters without the need for handling of loose components other than thecutter itself.

This object can be achieved by the provision of a seat at the end partof the shaft. The seat provides positioning of and a stable support fora cutter in at least two of the principal directions utilized in themachining operation, so that the stresses imposed on the cutter duringsuch machining are transferred in an effective fashion to the shaft. Atleast one tightenable fastening device is arranged on the shaft andengages with the cutter after tightening so as to force it against atleast one surface on the seat. The fastening device is intended toengage stop parts on the cutter only after the cutter, throughdisplacement of the cutter relative to the seat on the shaft and whilstthe cutter is still in contact with the seat, has reached its operatingposition.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in more detail below with reference to theaccompanying drawings, in which:

FIG. 1 is a side elevational view from the side of the end part of afirst embodiment of a tool arranged in accordance with the invention;

FIGS. 1A and 1B are enlarged views of portions of the tool of FIG. 1within the 1A and 1B lines of FIG. 1;

FIG. 2 is a front elevational view of the same tool;

FIG. 3 is a cross-sectional view taken along the line A--A in FIG. 2;

FIG. 4 is a cross-sectional view taken along the line B--B in FIG. 2;

FIG. 5 is a side elevational view of a modified embodiment of a cutterviewed from the side facing towards the shaft;

FIG. 6 is a side elevational view of the cutter in accordance with FIG.5 viewed from the side on which the cutting edge projects;

FIG. 7 is a side elevational view of the cutter in accordance with FIG.5 viewed from the outward-facing side;

FIG. 8 is a cross-sectional view taken along the line A--A in FIG. 7;

FIG. 9 is a cross-sectional view taken along the line B--B in FIG. 7;and

FIG. 9A is a cross-sectional view of a support shaft upon which thecutter of FIG. 9 can be fitted.

DETAILED DESCRIPTION OF THE INVENTION

The numeral 1 is used to designate a shaft 1 of a tool holder, which atits end is intended to carry a tool, more specifically, a cuttergenerally designated by 2. The tool 2 in question here is intended forturning in restricted spaces, for example, inside a hole, or in atubular workpiece or the like.

The shaft 1, which may be of circular cross-section along a further part3 indicated in FIG. 2 by a dashed and dotted line, exhibits a thinnerend part 4 of non-round cross-section produced by machining one sidethereof at its end surface 5. Arranged on or at the end surface 5 is atransverse groove 6 terminated by a curved end wall 7. Situated next tothe transverse groove 6 in a partially overlapping relationship is acircular recess 8 with a coaxially threaded central bore 9 (FIG. 4)arranged in the longitudinal direction of the shaft 1.

The cutter 2 is bar-shaped with an essentially rectangular cross-sectionand has a base part 13 with a rounded inner end 10 and a laterallydisplaced projection 12 at the other end for supporting a cutting edge11. A corner of the base part 13 is chamfered in connection with theinner end 10 of the cutter 2 so as to produce an inclined surface 14. Asshown in FIG. 4, the base part 13 has an opposite corner, which connectsbottom and side surfaces 15 and 16 of the cutter 2 and exhibits a smallchamfer 17 providing a longitudinal clearance between bottom and sideabutment walls 18 and 19 of the transverse groove 6 and the bottom andside surfaces 15 and 16 of the cutter 2. Referring to FIGS. 2 and 3,shallow recesses 20 and 21 are arranged on the aforementioned bottom andside surfaces 15 and 16 of the cutter 2, so that only end heels 22 and23 remain. The purpose of the chamfer 17 and the aforementioned heels 22and 23 is to permit the cutter to rest in a stable fashion against thewalls 18 and 19 of the groove 6.

Referring again to FIG. 4, a threaded fastening element, which isdesignated by 24, in the form of a screw has a threaded shaft part 25which engages with the threaded central bore 9, a cylindricaltransitional part 26 and a cylindrical head 27 with a frustoconicalunderside 28 forming essentially the same angle with the longitudinalaxis of the supporting shaft as the inclined surface 14 on the cutter 2.

When installing a cutter 2, the fastening element 24 must be loosenedslightly so that the inner end 10 of the cutter 2 can be displacedlaterally into the groove 6 for such a distance that it bottoms againstthe curved end wall 7 of the groove so inclined surface 14 is positionedbeneath the inward-facing frustoconical surface 28 of the screw head 27.As the screw 24 is tightened, the frustoconical surface 28 will engagewith the inclined surface 14 of the cutter 2 and will force the cutterinwardly so that the end heels 22 and 23 come into stable contact withthe bottom and side abutment walls 18 and 19 of the groove 6.

The fastening element may have a right-hand or a left-hand thread,depending on the intended working direction of the cutting edge 11, sothat as vibrations arise, the fastening element 24 does not exhibit atendency to turn in a direction which causes the cutter 2 to move out ofthe groove 6. The fastening element 24 may have a left-hand thread inthe embodiment shown in FIGS. 1-4.

The present invention provides simple handling which facilitates cutterreplacement to a considerable degree. It will be appreciated by thoseskilled in the art that the present invention is in no way more bulkythan the previously disclosed designs.

A second embodiment of the invention is illustrated in FIGS. 5-9 anddiffers purely in terms of its design from the previously describedembodiment. It can be used for the machining of holes and the like witha diameter only slightly exceeding the diameter of the shaft of the toolholder.

The cutter in accordance with FIGS. 5-9, which is generally designatedby 32, includes circular main part 33 and an axially displacedessentially radially extending projection 34, which supports a cuttingedge 35. A side 36 (FIG. 9) facing away from the shaft designated by 31exhibits a transcurrent hole with an essentially round hole part 37situated eccentrically or in a radially offset fashion away from theside with the projection 34, and a hole part 38 integral with the holepart 37 and similarly transcurrent, although centrally situated and witha smaller diameter or area than the hole 37, which the hole part 38 issurrounded by a countersunk part 39 (FIG. 7) arranged concentricallyaround it, which extends forwards as far as the edge of the hole part37. The countersunk part. 39 forms a step-like edge around the centrallysituated hole part 38.

The side of the cutter 32 facing towards the supporting shaft 31, whichcan be appreciated most clearly from FIGS. 5, 6, 8 and 9, exhibits aplane central surface part 40, which encloses the major proportion ofthe central hole part 38 and in so doing terminates at the further holepart 37. Situated radially outside the surface part 40 is a conicallytapered part 41 with a top angle of the order of 140°, which is alsointersected by the larger hole part 37. A heel 42, the outward-facingside of which lies in the same plane as the plane central surface part40, extends over the conically tapered part 41 in the direction of thecutting edge 35 and the projection 34. The heel 42 thus exhibitsessentially parallel triangular lateral surfaces.

The end part of the supporting shaft 31 for the cutter 32 is executed ina complementary fashion and has a central threaded bore 43 surrounded bya plane annular surface 44, to which an enclosing inclined surface 45 isconnected. The inclined surface 45 is interrupted by a groove 46 with anoutwardly increasing depth adapted to the form of the heel 42.

When fitting a cutter 32 to the supporting shaft 31, a screw such asthat indicated in FIG. 1 with the designation 24 must be unscrewed for asufficient distance to permit the screw head to be introduced throughthe larger hole part 37, i.e. with the cutter 32 in a laterallydisplaced position. The cutter 32 is then centered on the end of thesupporting shaft 31 by displacing the shank of the screw into thesmaller hole part 38, in conjunction with which the heel 42 is fitted atthe same time into the groove 46, which positions the cutter 32 in sucha way as to prevent it from rotating about its center. Once the cutter32 has reached the indicated position, the screw is tightened. Removaltakes place in the reverse sequence.

The interaction between the plane and conical surfaces and therotational stabilization by means of the heel 42 mean that the cutter 32is fixed in a stable fashion, and that the desired distribution offorces is obtained.

The invention is not limited to the embodiments shown above but can bevaried within the framework of the following patent claims.

It is claimed:
 1. Arrangement for tools for use in a cutting machineoperation, in particular, for machining in restricted spaces such asinternally in holes and inside hollow workpieces, comprising:(a) aholder shaft having one free end with a free end face; (b) a cutterholder on said free end of said holder shaft and being provided withboth a transverse groove dimensionally sized to receive a cutter insertand a threaded bore for receiving a threaded fastening device, saidtransverse groove located on said free end face of said holder shaft andbeing defined at least partially by at least two abutment surfaces, saidtransverse groove arranged adjacent said threaded bore; (c) a cutterinsert arranged in said transverse groove of said cutter holder, saidcutter insert having at least two engagement portions in contact withsaid abutment surfaces of said cutter holder so as to prevent movementof said cutter insert relative to said cutter holder caused by stressesduring the cutting machine operation, each of said engagement portionsof said cutter insert includes a long shallow recess separatingsupporting heels adjacent edges of the respective engagement portion forproviding a stable movement-free clamping of said cutter insert towardssaid abutment surfaces, said cutter insert also being provided with anoutwardly facing contact surface arranged to be engaged by a threadedfastening device located in said threaded bore at said free end of saidholder shaft so as to stabilize said cutter insert; and (d) a threadedfastening device having a threaded shaft portion in said threaded boreof said cutter holder, said threaded fastening device having acylindrical head and, between said cylindrical head and said threadedshaft portion, a contact surface inclined towards said screw shaftportion, said threaded fastening device moveable between a tightenedposition with said inclined contact surface of said threaded fasteningdevice engaged with said contact surface of said cutter insert to fixsaid cutter insert in said transverse groove of said cutter holder and aloosened position in which said cutter insert is freely moveable in saidtransverse groove.
 2. The arrangement in accordance with claim 1,wherein said outwardly facing contact surface of said cutter insert isinclined essentially at the same angle as said inclined contact surfaceof said threaded fastening device.
 3. The arrangement in accordance withclaim 1, wherein said inclined contact surface of said threadedfastening means has a frustoconical shape.
 4. The arrangement inaccordance with claim 1, wherein said cutter holder has a recess merginginto said threaded bore, said cylindrical head of said threadedfastening means is dimensionally sized for mating engagement with saidrecess.
 5. The arrangement in accordance with claim 1, wherein saidabutment surfaces of said cutter holder are arranged along axial andradial planes of said holder shaft.